You should avoid Window Cleaner as it contains a lot of water which will get into the cracks and further lift the paint or cause the wood grain to warp up.
You can always treat the painted playfield surface just like a Car finish (minus the soap and water cleaning). Most car wax product from abrasive cleaner to mild pure Carnuba waxes will work on a pinball playfield, Of course, you may want to avoid the very abrasive cleaners as they will take off too much paint if you are not careful.
You should also avoid any product that contains Ammonia to clean the plastics as it will ultimately yellow them.
That large crack down the left center of the playfield is where the top veneer was joined in the making of the plywood. Not too much you can do other than touch up and clear coating.